Ukraine President Volodymyr Zelensky on Thursday told European leaders that "delays" sending fighter jets and long-range missiles could extend the war, after he paid a visit to the frontline southern region of Kherson.

On the train home from the war-ravaged areas, Zelensky gave an emotional account of what he had seen as he addressed a summit of his EU counterparts gathered in Brussels via video link, an EU official said.

His demands came after Oleksandr Syrsky, commander of Ukraine's ground forces, said he planned to take advantage of the fact that Russian troops were "exhausted" near Bakhmut, the scene of the longest and bloodiest battle since the Russian invasion last year.

Bakhmut -- an eastern town which once had an estimated population of around 70,000 people -- has virtually emptied of civilians over months of fierce fighting between Russian and Ukrainian forces.

"The aggressor has not given up hope of taking Bakhmut at all costs despite losses in manpower and equipment," said Syrsky.

"Sparing nothing, they are losing significant strength and becoming exhausted.

"Very soon we will take advantage of this opportunity, like we did near Kyiv, Kharkiv, Balakliya and Kupiansk," he added, referring to successful Ukrainian counteroffensives last year.

Both sides have invested heavily in the fight, even though analysts say the city has little strategic value.

The head of Russia's Wagner mercenary group said this week that his forces were in control of around 70 percent of the city. A Russian aide in the wider Donetsk region has said the city was "practically surrounded".

- 'Returning' to Kherson -

On Thursday, Zelensky said he was on a "working trip to Kherson region" -- the southern region still partly controlled by the Russians, who are dug in on the eastern bank of the Dnipro river and routinely shell Kherson city, killing civilians.

Ukrainian forces recaptured Kherson city, the administrative centre of the southern region, last November following a strategic withdrawal of Russian forces.

Zelensky said his visit included one village where "houses and civilian infrastructural facilities were damaged" as a result of Russia's invasion.

He said local authorities were restoring essential services such as electricity and water in the village and rebuilding a medical centre.

"People are returning," he said in the post on social media Thursday. "I talked to the locals about their problems and needs," he added.

Kherson, a gateway to the Black Sea and the Sea of Azov, was captured easily and early by Russian forces in the early days of their February 2022 invasion.

Russian President Vladimir Putin claimed to have annexed Kherson and three other regions in Ukraine last September, despite not having full military control over any of them.

On Thursday, Ukraine's defence ministry said Russian troops had withdrawn from the southern city of Nova Kakhovka in the Kherson region, but quickly backtracked and said the report was a mistake.

Zelensky, in a separate post, said he had held a coordination meeting with officials and discussed de-mining and reconstruction in recaptured territory.

The head of Kherson's regional military administration, Oleksandr Prokudin, said Russian forces had killed one person and wounded two others over the last 24 hours.

Meanwhile EU chief Ursula von der Leyen announced Thursday she would help organise a conference on securing the return of Ukrainian children taken to Russia during the ongoing conflict.

Last week, the International Criminal Court issued an arrest warrant accusing Putin of war crimes for overseeing the deportation of Ukrainian children. More than 16,000 have been taken to Russia since the invasion, according to Kyiv.

- Uranium ammo -

On Monday, British junior defence minister Annabel Goldie confirmed the UK would provide Ukraine with ammunition containing depleted uranium -- making it heavier and better at penetrating steel.

NATO chief Jens Stoltenberg on Thursday dismissed Russian complaints over the move after Moscow warned it would be a "serious escalation" of the crisis in Ukraine.

"NATO allies are following international rules and international law in everything they do in their support for Ukraine," Stoltenberg told AFP when asked about the British plans and Russian complaints.

"The dangerous thing is the war, which is taking thousands of lives," he said at the operational launch of a new fleet of NATO-EU air-refuelling planes at a Dutch airbase.

"The most important thing that can be done to reduce risks is for President Putin to stop the war."